Materials Literature
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A method of describing the nonlocality of exchange and correlation energy and potential, which gives the correct long-range imagelike behaviour, is adopted in a self-consistent calculation of a solid surface in the framework of the jellium model. The exchange-correlation potential V xc ( z ), within the approximation…
Transient-photocurrent measurements in glassy ${\mathrm{As}}_{2}$${\mathrm{Se}}_{3}$ reveal an accurate power-law behavior spanning more than eight decades of time. In the multiple-trapping model this requires a density of valence-band-tail states varying exponentially with energy over almost five decades. The accurac…
Time-of-flight neutron diffraction data from a single crystal of K0.26WO 3 were refined with space group P63 using only l = 2n reflections (R(F) = 0.051 ). The odd-I data were not included in the refinement because of poor agreement with the structural model, indicating that the model is correct for a superposition of…
A detailed temperature-dependent study of the Raman spectra of oriented single crystals of NH4ClO4 is reported in the spectral regions of lattice modes and internal vibrations of the ClO−4 and NH+4 ions between 10 and 300 K. The internal modes of the ClO−4 ions show splitting into several components due to site and co…
All ZnS polytypes identified so far are listed; their Zhdanov elements show some peculiar statistical characteristics, which are attributed to their formation mechanism. During the cooling down of the crystals hexagonal domains become less and less stable while the stability of cubic domains increases. Transformations…
The local-density supercell impurity approach is used to calculate the excitation spectra due to the emission and absorption of a $3d$ electron in the Mott insulator NiO. Good agreement is found with both photoemission (PES) and inverse photoemission [bremsstrahlung isochromat spectroscopy (BIS)] data. In particular,…
The reaction of phosphine PH3 and diborane B2H6 on Si(100) surfaces was studied by surface analytical techniques in relation to the in situ doping process in the chemical vapor deposition of silicon. Phosphine chemisorbs readily either nondissociatively at room temperature or dissociatively with the formation of silic…
We have used x-ray and electron diffraction to study the icosahedral phase in rapidly quenched alloys of Al with Mn, Re, Cr, Ru, V, Mo, and W. We also find negative results in searches for the icosahedral phase in various other transition-metal alloys. Addition of small amounts of Si and Ru to Al-Mn and Al-Cr alloys a…
The complex refractive index N(ω)=n+ik and the complex dielectric constant ε(ω)=ε1+iε2 are presented for diamondlike amorphous carbon (a-C) films in the photon energy range 0.5–7.3 eV. The effective number of valence electrons neff per carbon atom, the static dielectric constant ε0,eff, and the energy loss function Im…
Inelastic scattering of electrons by small metal particles is investigated with full inclusion of spatial dispersion effects. In sharp contrast to results obtained from classical studies, based on the use of a local dielectric constant, the differential cross section for larger collection angles is rather diffuse beca…
The frequency and temperature dependence of the elastic moduli of a number of commercially available polymers has been studied in the temperature range of 0–35 °C and for frequencies 102–106 Hz. Away from transitions a significant new relationship has been obtained, i.e., the Young’s modulus of these polymers is propo…
The luminescence spectrum of ${\mathrm{SrTiO}}_{3}$ from 1.6 to 3.2 eV has been studied as a function of time elapsed after excitation. A broad emission band with maximum intensity at 2.44 eV can be observed. The shape of this band, including some fine structure, can be reproduced by the Huang-Rhys model for excitatio…
It has been found that the dielectric capacitance response of doped silica glasses measured in the frequency range 10 -3 -10 5 Hz for temperatures between 500 and 1100K displays anomalous thermally activated resonance-type behaviour. This response is linked to time domain oscillations reported in similar materials. It…
The adequacy of the Callaway integral (1959, 1974) and the Leibfried-Schlomann formula (1979) for describing the pressure dependence of the thermal conductivity of insulators is investigated. It is concluded that, overall, the Leibfried-Schlomann formula and the Callaway integral offer roughly the same agreement betwe…
The electronic properties of the ferrous ion in (Fe(H 2 O) 6 )(NH 4 ) 2 (SO 4 ) 2 are investigated using far-infrared (FIR) Fourier transform spectra and FIR EPR measurements at low temperatures in the energy range from 8 to 100 cm -1 . Several absorption lines can be identified to originate from electronic excitation…
Polarised luminescence spectra of Cr 3+ -doped beta -alumina crystals were taken at temperatures between 78 and 295K. From luminescence excitation spectra the energy level scheme of the Cr 3+ ion is obtained. This turns out to be very similar to that of ruby, with the Cr 3+ ion substitutional for the Al 3+ ion in the…
Neutron and X-ray diffraction measurements of liquid sulphuric acid are reported. The aim of the present work is to study the arrangement of the hydrogen atoms in the liquid in comparison with the solid phase. By employing both experimental techniques, the localization of both heavy atoms and hydrogen is possible. We…
The electronic structure of ferroelectric LiNbO 3 at room temperature has been investigated using the X alpha molecular orbital method applied to a NbO 6 cluster of C 3v symmetry. The total and partial densities of states associated to the O 2p valence band built up from the X alpha eigenvalues are compared with XPS a…
Intense luminescence due to the 2 F 5/2→2 F 7/2 transition, near 1μm, is observed when the elpasolites Cs2NaHoCl6 and Cs2NaNdCl6 are doped with Yb3+ and excited by 488 nm or 514 nm argon ion laser radiation respectively. The mechanism of energy transfer has been studied for Cs2NaHoCl6: YbCl3- 6 using temperature, conc…
Layer-by-layer alternating surface reconstructions of Si(001) 2×1 and 1×2 have been observed for the first time using reflection high-energy electron diffraction (RHEED) during molecular beam epitaxy. RHEED intensity oscillations of the specular beam and two kinds of reconstruction related spots have been monitored si…